Cooling system for machine tools



P 1947. cPF. CHARLTON ET AL p 2 ,8

' COOLING SYSTEM FOR MACHINE TOOLS Filed Jan. 19, 1945 Patented'sept. 2,1947 I UNITED STATES PATENT OFFICE COOLING SYSTEM FOR MACHINE TOOLSCharles F. Charlton and Mark A. Palmer, J12,

' Manchester, Conn;

Application January 19, 1945, Serial No. 573,608

1 Claim. (01. 51 267) This invention relates to a novel and superiorcooling system for machine tools, such as grinding machines, millingmachines, etc. The grinding or cutting contact of such tools with theWork generates a considerable amount of heat and a circulatin flow ofcooling liquid is commonly provided over the tool and work for thepurpose of keeping the temperature reduced to a safe maximum. It isdesirable that foreign particles shall be separated from the spentliquid before it is again returned to the work and that the liquid shallbe maintained below a predetermined maximum temperature.

In machines heretofore employed the spent liquid has been returned to asettling tank where the solids are precipitated and the liquid cooledbefore the latter is again returned to the work. This system ofmaintaining the liquid at predetermined temperature has proveninefficient due to the accumulation of solids on the refrigeratingplates employed in the tank. Our invention contemplates the eliminationof this difiiculty by first separating the solids from the spent liquidby precipitation or otherwise and thereafter bringing the liquid to andmaintaining it at the desired temperature by passing it through anenclosed channel including a, refrigerating medium on its way back tothe work. The production of such an improved method of circulatincooling liquid to machine tools and providing such liquid in clean andpredetermined temperature condition to the work therein comprises theprimary object of the invention.

The work operated on by grinding machines is required to be finished toa small tolerance and unless the work is kept at substantially uniformtemperature during the grinding operation its expansion and contractionprevents the maintaining of such tolerance. In apparatus heretoforeemployed the temperature of the cooling liquid has varied as much as 15and has been particularly affected by the gathering of sediment to aconsiderable thickness on the cooling system, thereby forming aninsulation rendering the cooling effect very inefficient. We havediscovered that by first removing the sediment and solids from theliquid and thereafter passing the clean liquid to the Work through anenclosed channel including a refrigerating unit maintained atpredetermined temperature we are able to keep the work at a plus orminus temperature within two degrees. The novel method resulting in thisincreased efliciency comprises an important object of our invention.

These and other features of the invention will be best understoodandappreciated from the following description of a preferred embodimentthereof selected for purposes of illustration and shown in theaccompanying drawing in which the one figure in the drawing is anelevation, partly broken away, of a machine embodying our invention.

In the drawing we have illustrated a grinding machine it including agrinding wheel l2. A liquid coolant is conducted to the wheel and workfrom a nozzle I in communication with a pipe it, the flow beincontrolled by a valve l8. A coolant reservoir 23 is provided beneath thegrinding wheel to receive the spent coolant. It is desirable thatforeign particles, particularly including those picked up from the work,should be removed before the coolant is returned to the tool and forthis purpose we have illustrated the reservoir as divided into aplurality of compartments 22, 23 and 24. The spent coolant flows fromthe tool into the first compartment 22 Where most of the particlessettle before the coolant flows over the baffle 25 into the compartment23. Further settling of any remaining particles takes place incompartment 23 before the coolant flows over the baffle 26 into thecompartment 24. The resulting relatively clean coolant is circulatedfrom the compartment 24 back to the tool.

Efficient operation requires that the temperature of the coolant shallbe at or below a predetermined maximum when it reaches the tool and workand the primary object of our invention resides in an improved methodfor elliciently maintaining such temperature within predeterminedlimits. To this end we pass the clean coolant from the compartment 2:3through a refrigerating path on its return to the tool. As illustratedin the drawing, this path includes a plurality of pipes or tubes 28surrounded by a refrigerating medium of predetermined capacity andtemperature within a cylindrical heat exchanger 3B.

Mounted on the reservoir is a pump 32 operated by a motor 36 andarranged to pump thecoolant from the compartment 24 through pipes 38,38, V

28 and Hi to the nozzle It. An economizer In is preferably employed inconnection with the refrigerating system. A compressor (not illustrated)maintains a suction on the line 42 which passes in the form o f-a coil44 back to the chamber 39 at 46. The vapor thus drawn from the chamheris compressed to a liquid and returned through a pipe 48 to and througha coil 48 within the pipe of coil 4d and from thence through a pipe 50to the bottom of the chamber 30. A thermoworking operations thereon,which consists in static expansion valve is provided at 52 and isconducting spent cooling liquid from the work connected by a tube 54 toa controlling expansion to a separating chamber, separating the detritusbulb at 56 whereby automatically to maintain a solids from the liquid inthe separating chamber, predetermined temperature within the chamber 5conducting the separated liquid through a refrig- 30. The passage of theliquidrefrigerant through erating device maintained at a constant andthe relatively cooler vapor refrigerant within the definite temperaturethereby cooling the sepcoils substantially. cools the reirigerartrliquigi to arated liquid; to;. a predetermined temperature, therequireddegre Orbits return {cathechamber and discharging said; liquid 7at; said predeter- 30. A refrigerant liquid level is maintained in 10mined temperature onto the work.

the chamber 30 substantially as indicated at 58;; CHARLES F. CHARLTON.It will be apparent that the coolant is cooled MARK A. PALMER, JR.

with maximum efficiency as it passes-throughthe several pipes 28 on itsreturn from the .com, 7 REFERENCES CITED Partment 24 t0 the 1 a it Wi lbe furthgrrhgl'e 15;, Thejollowing references are of record in theapparent that the cooling system is adaptedto file of this patent:

operate and continue to operate with maximum-- efficiency on the coolantwhich is substan ially v UNITED STATES PATENTS freed from foreignparticles before being cir-' Number Name Date culated through therefrigerating path, 9 ,7 MiSkOlCZY ----r---- p 02 Having'thus disclosedour invention what, we 2,132,952 Todd etal. Dec.- 12, 1939 claim as newand desire to secureby Letters e et a Patent oi the United States is:403,030; Bauer May '7; 1889 A method of producing work-toclosetolerances 1,455,187 Brown May 15, 1923 in a machine tool bymaintaining a predetermined 25 1,938 ,8'75 1 Stratton Dec. 12,- 1933constant temperature in the-workpiece during

